Essential Role of Lysophosphatidylcholine Acyltransferase 3 in the Induction of Macrophage Polarization in PMA‐Treated U937 Cells

Abstract

Lysophospholipid acyltransferases (LPLATs) regulate the diversification of fatty acid composition in biological membranes. Lysophosphatidylcholine acyltransferases (LPCATs) are members of the LPLATs that play a role in inflammatory responses. M1 macrophages differentiate in response to lipopolysaccharide (LPS) and are pro-inflammatory, whereas M2 macrophages, which differentiate in response to interleukin-4 (IL-4), are anti-inflammatory and involved in homeostasis and wound healing. In the present study, we showed that LPCATs play an important role in M1/M2-macrophage polarization. LPS changed the shape of PMA-treated U937 cells from rounded to spindle shaped and upregulated the mRNA and protein expression of the M1 macrophage markers CXCL10, TNF-α, and IL-1β. IL-4 had no effect on the shape of PMA-treated U937 cells and upregulated the M2 macrophage markers CD206, IL-1ra, and TGF-β in PMA-treated U937 cells. These results suggest that LPS and IL-4 promote the differentiation of PMA-treated U937 cells into M1- and M2-polarized macrophages, respectively. LPS significantly downregulated the mRNA expression of LPCAT3, one of four LPCAT isoforms, and suppressed its enzymatic activity toward linoleoyl-CoA and arachidonoyl-CoA in PMA-treated U937 cells. LPCAT3 knockdown induced a spindle-shaped morphology typical of M1-polarized macrophages, and increased the secretion of CXCL10 and decreased the levels of CD206 in IL-4-activated U937 cells. This indicates that knockdown of LPCAT3 shifts the differentiation of PMA-treated U937 cells to M1-polarized macrophages. Our findings suggest that LPCAT3 plays an important role in M1/M2-macrophage polarization, providing novel potential therapeutic targets for the regulation of immune and inflammatory disorders.

Heparanase regulates the M1 polarization of renal macrophages and their crosstalk with renal epithelial tubular cells after ischemia/reperfusion injury

“…M2 macrophages produce anti-inflammatory and proregenerative mediators that alter the expression of several genes in parenchymal cells to promote tissue regeneration and repair (55,56). The initial M2 polarization we observed was supported by earlier in vivo studies showing the release of specific cytokines (IL-4 and IL-10) during allograft processes characterized by the accumulation T helper 2 and regulatory T lymphocytes, probably enhanced by the infiltration of these cells along with M1 macrophages after the phagocytosis of apoptotic cells, and the production of cytokines such as colony-stimulating factor 1 by tubular cells (57). The inhibition of HPSE by SST0001 did not reduce the M2 macrophage population or the expression of the M2 markers Arg1 and MR.…”

Bu Fei Decoction attenuates the tumor associated macrophage stimulated proliferation, migration, invasion and immunosuppression of non-small cell lung cancer, partially via IL-10 and PD-L1 regulation

“…Taniguchi et al (7) used PMA and IL-4 to treat U937 cells and obtained M2-polarized TAMs. We treated U937 cells as described above.…”

“…Macrophages originate from blood monocytes, and there are two main classes of macrophages: classically activated macrophages (also called M1) and alternatively activated macrophages (M2) (6). When exposed to lipopolysaccharide (LPS) or interferon-γ (IFN-γ), macrophages are polarized into M1 macrophages; whereas interleukin-4 (IL-4) or interleukin-13 (IL-13) exposure can polarize them into M2 macrophages (7). M1 macrophages generally exhibit microbicidal activity and have pro-inflammatory phenotype.…”

Liver-specific knockdown of long-chain acyl-CoA synthetase 4 reveals its key role in VLDL-TG metabolism and phospholipid synthesis in mice fed a high-fat diet

“…It has been demonstrated that the phospholipid remodeling enzyme lysophosphatidylcholine acyltransferase 3 (LPCAT3) is a critical determinant of TG secretion due to its unique ability to catalyze the incorporation of arachidonate into membranes, which impacts membrane lipid mobility in living cells (31,39,43,54). LPCAT3 catalyzes the formation of phosphatidylcholines (PC) from saturated lysoPCs (LPC), inserting PUFAs at the sn-2 position (40, 42).…”